Support android as a target platform.

grit/node/base.py

Index: grit/node/base.py
diff --git a/grit/node/base.py b/grit/node/base.py
index e38ec0d0aeffedf6f53b8580112771fcbf4a2234..3d23c6a3aa0771d232432bc781b6567de1d8e9b8 100644
--- a/grit/node/base.py
+++ b/grit/node/base.py
@@ -458,8 +458,10 @@ class Node(object):
         'is_linux': target_platform.startswith('linux'),
         'is_macosx': target_platform == 'darwin',
         'is_win': target_platform in ('cygwin', 'win32'),
-        'is_posix': (target_platform in ('darwin', 'linux2', 'linux3', 'sunos5')
-                     or 'bsd' in target_platform),
+        'is_android': target_platform == 'android',
+        'is_posix': (target_platform in ('darwin', 'linux2', 'linux3', 'sunos5',
+                                         'android')
+                    or 'bsd' in target_platform),
         'pp_ifdef' : pp_ifdef,
         'pp_if' : pp_if,
     }